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Nissan Altima P0123: TPS Circuit “A” → High Input


P0123 Nissan Altima

P0123 is a relatively common OBD-II code. It is generic, meaning it has the same meaning for the Nissan Altima as it does for any other vehicle. It is an OBDII code that refers to problems with the Throttle Position Sensor (TPS). This is a relatively serious problem, as it can leave your vehicle stranded or very limited.

The throttle position sensor controls the angle of the throttle blade. When the throttle is closed, the signal sent to the ECM is about 0.45 volts. When the throttle is fully open, the signal will be about 5 volts. P0123 occurs when your Altima’s TPS voltage is above the upper operating range.

P0123 occurs when your Altima’s TPS voltage is above the upper operating range.

Nissan Altima: P0123 Symptoms

Nissan Altima Diagnostics P0123

The symptoms of P0123 are going to vary by year and model, but they are certainly going to cause noticeable changes in the way your Altima runs. Without a proper TPS signal, your Altima will compensate in several ways.

These are the most common symptoms of P0123:

  • throttle response– Your Altima may not respond slightly to the accelerator. This limited power is a safety mechanism so that the vehicle can move, but not super fast. Since the ECM doesn’t really know the throttle response when you step on the gas.
  • Idle speed problems– Without knowing exactly where the throttle is, the Altima’s computer may have difficulty achieving the correct idle speed.

Different model years and engine combinations will experience different symptoms.

P0123 Diagnostic: Nissan Altima

The OBDII code P0123 is a serious problem that requires close attention. Diagnosing it can be difficult without a good scanner and knowledge of what you are doing. Here is a YouTube video showing how to diagnose this code with a scanner.

A good mechanic will use a scanner to diagnose when the codes were set and reset them. Then they will see if the problem appears again.

If everything checks out and the code comes back, you can go ahead and replace the TPS sensor in question. Most of the time, the problem when P0123 is thrown will be the TPS sensor itself. It no longer registers the force with which the fuel pedal is depressed.

Causes P0123 – Altima

There are a few problems that cause P0123. Are:

  • Wiring problems– Since the TPS is so accessible, a good starting point is to do a visual inspection of the wiring and the wire harness leading to it from the engine computer. Is there any damage? Here is a great article on diagnosing a short circuit.
  • bad TPS– There is a video on YouTube on how to diagnose a TPS sensor. If you need one they are pretty cheap on Amazon.
  • The TPS is not mounted correctly– Although not very common, it is possible that the TPS sensor has not been mounted correctly. If you have recently replaced it and you get P0123, it is a good idea to check the instructions for the replacement sensor and see if they mention this.

Nissan Altima P0123 Conclusion

Diagnosing the problem with a scanner or having a mechanic take a look can save you the expense of purchasing a TPS sensor that your Altima doesn’t really need.

Good luck diagnosing P0123 on your Nissan Altima. If there is anything you want to add, leave a comment below. Thank you for reading.


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